Avian infectious coryza is one of the most important respiratory diseases caused by infection with A.pg. Chicken suffering from avian infectious coryza shows cardinal symptoms of a running nose, swelling of the face and epiphora. Avian infectious coryza brings about a great economical damage since it leads to decrease in the breeding rate of chicken, retarding of egg laying, decrease in egg production or failure of egg laying.
Page et al. classified A.pg into three serotypes A, B and C (see e.g. Non-patent reference 1) and Sawata et al. classified A.pg into two serotypes 1 and 2 (see e.g. Non-patent reference 2). Thereafter, Kume et al. reported that serotype A by Page et al. corresponds to serotype 1 by Sawata et al. and serotype C by Page et al. corresponds to serotype 2 by Sawata et al. (see e.g. Non-patent references and 4). Today, it is established that main causative agents of avian infectious coryza are A.pg serotype A (hereinafter also referred to as “A.pg-A”) and A.pg serotype C (hereinafter also referred to as “A.pg-C”).
For prevention of avian infectious coryza, an inactivated vaccine has hitherto been used widely which is obtained by inactivating the cells of A.pg-A or A.pg-C with formalin, thimerosal and the like. However, adverse side effects caused by such an inactivated vaccine have been an issue as it has been reported that local necrotic lesions are formed in the inoculated chicken when the vaccine is administered (see e.g. Non-patent reference 5). Under the circumstances, attempting to develop a safe vaccine, a recombinant vaccine has been investigated comprising a protective antigen against infection prepared by genetic recombination technique.
For instance, Tokunaga et al. isolated and identified a gene coding for an outer-membrane protein of A.pg-A (outer-membrane protein gene) and found that a peptide obtained by expressing a part of said gene (HPG3.5 kbp, HPG4.1 kbp) in E. coli is useful as a protective antigen against infection for avian infectious coryza. Furthermore, using said DNA fragment as a probe, they obtained an outer-membrane protein gene from A.pg-C and compared nucleotide sequences of open reading frame of the outer-membrane protein gene from A.pg-A and A.pg-C. As a result, they revealed that both nucleotide sequences had homology of about 80% as a whole, that a region of 3.4 kbp at the 5′-end (hereinafter also referred to as “Region 1”) and a region of about 1.2 kbp at the 3′-end (hereinafter also referred to as “Region 3”) had extremely high homology and that a region of about 1.5 kbp flanked by Region 1 and Region 3 (hereinafter also referred to as “Region 2”) had low homology (see Patent reference 1).
It is also reported by Noro et al. that the outer-membrane protein discovered by Tokunaga et al. is important as a protective antigen for avian infectious coryza. Noro et al. immunized chicken with peptides coded by DNA fragments of 4,801 by and 5,157 bp, which are parts of the outer-membrane protein gene from A.pg-A, to show that said peptides may induce HI antibody to A.pg-A and may have a vaccine effect (see e.g. Patent reference 2) and further reported that peptides coded by DNA fragments of about 5.1 kbp and 5.5 kbp, which are parts of the outer-membrane protein gene from A.pg-C, had similar function and effect (see e.g. Patent reference 3).
On the other hand, Yamamoto et al. employed a polypeptide coded by a DNA fragment of 2,016 bp, which comprises most of the outer-membrane protein gene from A.pg-A to show usefulness of said polypeptide (see e.g. Patent reference 4) but the nucleotide sequence of about 300 by at the 3′ end of the DNA fragment reported by them was extremely different from those shown by Tokunaga et al. and Noro et al.    Patent reference 1: WO98/12331    Patent reference 2: Japanese patent No. 4001117    Patent reference 3: JP 2008-156317    Patent reference 4: JP 2004-57078    Non-patent reference 1: Am. J. Vet. Res., 23:85-95, 1962    Non-patent reference 2: Jpn. J. Vet. Sci., 40:645-652, 1978    Non-patent reference 3: m. J. Vet. Res., 41:757-760, 1980    Non-patent reference 4: Am. J. Vet. Res., 41:1901-1904, 1980    Non-patent reference 5: Avian Dis., 15:109-117, 1971